A Second Slice of FPIES: A Single-Center Reappraisal of Pediatric FPIES.

BACKGROUND: Food protein-induced enterocolitis syndrome (FPIES) is being increasingly recognized as a non-IgE-mediated food allergy; however, it remains unclear if and how the presentation, diagnosis, and management of this disease has changed in recent years. OBJECTIVE: To reappraise the FPIES cohort at a large US pediatric tertiary referral center. METHODS: We performed a retrospective chart review of pediatric patients with FPIES (International Classification of Diseases, Tenth Revision code K52.21) diagnosed in our allergy/immunology clinics between 2018 and 2022. RESULTS: There were 210 children diagnosed with FPIES. Most were White (73.8%), non-Hispanic (71.4%), and male (54.3%) with private insurance (77.6%). Cow's milk was the most common food trigger (35.2%), with the earliest median age of onset of 5 months. The atypical FPIES rate was 13.8%. FPIES was accurately diagnosed in 54.3% at the first medical contact. The oral food challenge pass rate was 73.5%. The rate of trigger resolution at 36 months was 77%. CONCLUSIONS: By comparing trends from a previous and current FPIES cohort, we were able to assess the potential impact of various guidelines and practice changes on the diagnosis and management of FPIES at our center. Milk and oat surpassed rice as the most common FPIES triggers; peanut and egg emerged as new FPIES triggers; there was a shorter time to diagnosis and an increased rate of atypical FPIES. Our findings reflect earlier recognition of FPIES and prompt allergy/immunology referral from community physicians, implementation of recent medical society guidelines for infant feeding practices, and growing clinical expertise of allergists at our center.

A subset of high-titer anti-factor VIII A2 domain antibodies is responsive to treatment with factor VIII.

The primary B-cell epitopes of factor VIII (fVIII) are in the A2 and C2 domains. Within the C2 domain, antibody epitope and kinetics are more important than inhibitor titer in predicting pathogenicity in a murine bleeding model. To investigate this within the A2 domain, the pathogenicity of a diverse panel of antihuman fVIII A2 domain monoclonal antibodies (MAbs) was tested in the murine model. MAbs were injected into hemophilia A mice, followed by injection of human B domain-deleted fVIII. Blood loss after a 4-mm tail snip was measured. The following anti-A2 MAbs were tested: high-titer type 1 inhibitors 4A4, 2-76, and 1D4; 2-54, a high-titer type 2 inhibitor; B94, a type 2 inhibitor; and noninhibitory MAbs GMA-012, 4C7, and B25. All high-titer type 1 MAbs produced blood loss that was significantly greater than control mice, whereas all non-inhibitory MAbs produced blood loss that was similar to control. The type 2 MAbs were not pathogenic despite 2-54 having an inhibitor titer of 34 000 BU/mg immunoglobulin G. In addition, a patient with a high-titer type 2 anti-A2 inhibitor who is responsive to fVIII is reported. The discrepancy between inhibitor titer and bleeding phenotype combined with similar findings in the C2 domain stress the importance of inhibitor properties not detected in the standard Bethesda assay in predicting response to fVIII therapy.

Microglia and macrophages are increased in response to ischemia-induced retinopathy in the mouse retina.

PURPOSE: The ability of microglial cells (MG) and macrophages (MAC) to release cytokines, induce apoptosis, as well as perform phagocytic functions suggests a possible role in wound healing following oxygen-induced injury. This study was performed to determine the temporal and spatial expression of F4/80 (F4/80+) positive microglia/macrophages (MG/MAC) in areas of retinal damage in the mouse model of oxygen-induced retinopathy. METHODS: C57BL/6 postnatal day 7 (P7) mice were exposed to 75% O2 for 5 days (P12) then allowed to recover in room air. Hyperoxia-exposed (O2) mice (O2 refers to hyperoxia exposure from P7 to P12 only) were sacrificed on P12, P14, P17, and P21 and their eyes were examined. Localization of F4/80+ cells in FITC-dextran-perfused retinas allowed coordinate visualization of retinal vessels and MG/MAC via fluorescence microscopy. BrdU, a cellular proliferation marker, was injected intraperitoneally 1 h prior to sacrifice. Immunostaining was performed for a microglia and macrophage-specific antigen (F4/80) and BrdU. CCL2 (monocyte chemoattractant protein-1; MCP-1) expression was examined by quantitative real time reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: There was a marked increase (>500%) in MG/MAC in hyperoxia-exposed retinas on P17O2 and P21O2 compared to control retinas. At P17O2, MG/MAC were localized in areas of neovascularization (NV), revealing an intimate relationship between MG/MAC and neovascular tufts. However, P21O2 retinas demonstrated MG/MAC associated with avascular regions in the outer layers of the retina. Immunostaining for F4/80 and BrdU revealed rare co-localization in hyperoxia-exposed retinas. Real time RT-PCR results demonstrated increased expression of CCL2 in P14O2- and P17O2- exposed retinas. CONCLUSIONS: Our results suggest that resident retinal microglia proliferation occurs at a low frequency in response to injury in this model. The substantial increase in total F4/80+ cells in hyperoxia-exposed retinas in conjunction with the upregulation of CCL2 is consistent with recruitment of hematogenous macrophages into the retina. The temporal and spatial localization of MG/MAC adjacent to neovascular tufts suggests these cells are modulating the retinal response to ischemia-induced retinopathy.

Increased expression of chemokine KC, an interleukin-8 homologue, in a model of oxygen-induced retinopathy.

PURPOSE: The purpose of this study was to determine the retinal expression of angiogenic chemokines/cytokines in a mouse model of oxygen-induced retinopathy. METHODS: C57BL/6 (B6) mice were exposed to 75% oxygen from postnatal day 7 (P7) to P12 and then recovered in room air. Reverse transcription-polymerase chain reaction (RT-PCR) was used to determine relative mRNA levels of KC, macrophage inflammatory protein-2 (MIP-2), interleukin-1alpha (IL-1alpha), and interferon gamma (IFN-gamma). Immunohistochemistry was used to localize KC in the retina. IL-1alpha was also injected into the vitreous of mouse eyes, and KC expression was examined by RT-PCR, enzyme-linked immunosorbent assay (ELISA), and immunohistochemistry. RESULTS: KC expression at both the mRNA and protein levels was increased in P14, P17, and P21 of hyperoxia-injured eyes. KC immunoreactivity was localized along the nerve fiber layer and in radial Müller cell processes. IL-1alpha mRNA was modestly increased in hyperoxia-injured eyes on P14 and P17. INF-gamma mRNA was not detected in the retina. Adult mouse eyes injected with IL-1alpha demonstrated increased levels of both KC mRNA and protein, with KC immunoreactivity localized to Müller cell processes. CONCLUSIONS: Oxygen-induced injury to the developing retina results in the induction of the CXC chemokine KC at both the mRNA and protein levels during the peak time points of neovascularization, suggesting a possible role in the pathogenesis of retinopathy of prematurity.

Increased retinal neovascularization in Fas ligand-deficient mice.

PURPOSE: To investigate whether the absence of the Fas-Fas ligand system of apoptosis regulation affects hyperoxia-induced retinal vaso-obliteration and retinal neovascularization in a mouse model of oxygen-induced retinopathy. METHODS: C57BL/6 (B6) and congenic Fas ligand-deficient generalized lymphoproliferative disease (gld) mice were exposed to 75% oxygen from postnatal day (P)7 to P12 and then allowed to recover in room air. Eyes obtained from P7, P8, P10, P12, P14, P17, and P21, from both hyperoxia-injured and room air control animals were processed for histopathologic examination. Retinopathy was also qualitatively assessed in FITC-dextran perfused retinas by fluorescence microscopy. TUNEL assays were used to compare apoptosis in B6 and gld mice. Intraretinal blood vessel formation was quantitated by immunolabeling with an anti-type-IV collagen antibody. Retinopathy was further assessed by quantitation of preretinal neovascular nuclei on P17. RT-PCR was used to examine retinal expression of Fas and Fas ligand (FasL) over a time course of hyperoxia-induced retinopathy. RESULTS: In hyperoxia-injured mice, the same degree of vaso-obliteration was apparent on P8, P10, and P12 in B6 and gld mice. By P17, the hyperoxia-exposed FITC-perfused retinas of both strains exhibited preretinal neovascular tufts. However, P17 gld hyperoxia-exposed retinas exhibited approximately a 50% increase in preretinal neovascular nuclei compared with B6 mice. In addition, a subset of apoptotic cells located solely within the neovascular tufts on P17 were significantly decreased in hyperoxia-exposed gld retinas, compared with B6 control animals. RT-PCR showed an increase in the expression levels of Fas in both strains of mice as a result of hyperoxia-induced injury. CONCLUSIONS: These data suggest that the Fas-FasL interaction plays an important role in retinal neovascularization after hyperoxia-induced injury. The absence of functional FasL leads to an increased incidence of preretinal neovascular nuclei and decreased retinal apoptosis suggesting that this pathway may serve as a means of regulating endogenous endothelial cell populations in pathologic angiogenesis.